Cytotoxic ribonucleases with antitumor activity are mainly found in the oocytes and early embryos of frogs, and share sequence similarity with each other. They all belong to the RNase A superfamily but possess different cytotoxicities, base specificities and ribonucleolytic activities. RC-RNase 4, one of the five novel ribonucleases isolated from the oocytes of Rana catesbeiana, is a 106 amino ...

Escherichia coli RNase T, an RNA-processing enzyme and a member of the DEDD exonuclease superfamily, was examined using sequence analysis and site-directed mutagenesis. Like other DEDD exonucleases, RNase T was found to contain three conserved Exo motifs that included four invariant acidic residues. Mutagenesis of these motifs revealed that they are essential for RNase T activity, indicating th...

The 2-5A-dependent RNase (RNase L) is a tightly regulated endoribonuclease of higher vertebrates that is catalytically active only after engaging unusual effector molecules consisting of the 2',5'-linked oligoadenylates, p1-3A(2'p5'A)>/=2 (2-5A). Progressive truncations from either terminus have provided insight into the structure, function, and regulation of RNase L. We determined that deletio...

The control of mRNA stability is an important component of regulation in bacteria. Processing and degradation of mRNAs are initiated by an endonucleolytic attack, and the cleavage products are processively degraded by exoribonucleases. In many bacteria, these RNases, as well as RNA helicases and other proteins, are organized in a protein complex called the RNA degradosome. In Escherichia coli, ...

Disulfide bonds play important roles in the folding and stability of proteins and are evolutionarily conserved. A classic example is RNase A (also known as bovine pancreatic ribonuclease), which contains 4 conserved disulfide bonds among 8 cysteines. However, human RNase 8, a paralog of RNase A uniquely expressed in the placenta, has lost one of the conserved cysteines but gained another, when ...

RNase L, a principal mediator of innate immunity to viral infections in higher vertebrates, is required for a complete IFN antiviral response against certain RNA stranded viruses. dsRNA produced during viral infections activates IFN-inducible synthetases that produce 5'-phosphorylated, 2',5'-oligoadenylates (2-5A) from ATP. 2-5A activates RNase L in a wide range of different mammalian cell type...

RNA metabolism is a critical but frequently overlooked control element affecting virtually every cellular process in bacteria. RNA processing and degradation is mediated by a suite of ribonucleases having distinct cleavage and substrate specificity. Here, we probe the role of two ribonucleases (RNase III and RNase J) in the emerging model system Streptomyces venezuelae. We show that each enzyme...

RNase L and Ire1p are members of a superfamily of regulated endoribonucleases that play essential roles in mediating diverse types of cellular stress responses. 2'-5' oligoadenylates, produced in response to interferon treatment and viral double-stranded RNA, are necessary to activate RNase L. In contrast, unfolded proteins in the endoplasmic reticulum activate Ire1p, a transmembrane serine/thr...